The invention relates to an instrument for connecting a correction rod to a bone screw, in particular a pedicle screw in spinal surgery, said instrument having an axial longitudinal direction and comprising an external first housing part, which comprises a cylindrical hollow portion having an internal thread and a portion that is approximately the shape of a half-shell and that forms a first clamp leg, said instrument comprising an external second housing part, which is approximately the shape of a half-shell and forms a second clamp leg that is hinged on the first clamp leg so as to be pivotable in a limited manner about a pivot axis that extends orthogonally to the axial longitudinal direction, and said instrument comprising an adjustment part, which axially penetrates the external housing parts and is thus predominantly internal, and which comprises an external thread on one portion and can thus be screwed into the internal thread of the external first housing part, a proximal end of the adjustment part being manually graspable from outside the housing parts for this purpose, and said instrument comprising a rod pressure part, which can be axially placed against the correction rod and which is axially coupled to the adjustment part but can rotate about the axial longitudinal direction relative to the adjustment part, such that rotational movements of the adjustment part are not transmitted to the rod pressure part, and the clamp legs surrounding the rod pressure part in a shell-like manner and guiding same in a longitudinally slidable manner, said clamp legs each comprising a distal end and a proximal end, the relevant distal end engaging on the bone screw and the proximal end being actuatable by finger pressure of the operating surgeon.
An instrument of this kind is known from DE 10 2013 207 183 A1 by the applicant. In a previously known instrument of this kind, the first and second clamp legs each rest against a leg of an accommodation part, which is U-shaped when viewed from the side, of a pedicle screw when said pedicle screw is being gripped, such that the shell shapes of the clamp legs extend approximately concentrically to the legs of the U-shaped accommodation part in each case and provide between them the accommodation space, formed by the U shape, for a correction rod. The correction rod, or the longitudinal extension thereof, is therefore substantially parallel to the pivot axis of the joint of the two clamp legs of the instrument. However, this clamp joint requires a relatively large amount of installation space towards the pivot axis. As a result, the space next to the pedicle screw in question is limited in the direction of the longitudinal axis of the correction rod such that an adjacent pedicle screw cannot be readily gripped using another instrument at the same time.
The object of the present invention is to improve an instrument of the type mentioned with respect to the practical applicability thereof.